U.S. patent application number 10/726044 was filed with the patent office on 2004-08-05 for extrusion blow molded reusable storage containers with varying wall thickness.
Invention is credited to Rodi, Gina, Shepler, William, Skov, Erik.
Application Number | 20040149762 10/726044 |
Document ID | / |
Family ID | 32775897 |
Filed Date | 2004-08-05 |
United States Patent
Application |
20040149762 |
Kind Code |
A1 |
Shepler, William ; et
al. |
August 5, 2004 |
Extrusion blow molded reusable storage containers with varying wall
thickness
Abstract
An improved reusable storage container is disclosed with a
varying wall thickness. Specifically, the vertical corner sections
have a greater wall thickness than the side and end panels and,
possibly, the bottom panel. Further, the various corner sections or
corner junctions of the structure may also have a greater average
wall thickness than the vertical, side or end panels and, possibly,
the bottom panel. The improved container is fabricated using an
extrusion blow molding process with a shaped die in combination
with parison programming so that the thickness of the extruded
parison is non-uniform both radially and axially. An adjustable die
for carrying out the extrusion blow molding process is also
disclosed.
Inventors: |
Shepler, William;
(Brunswick, OH) ; Rodi, Gina; (Wooster, OH)
; Skov, Erik; (Akron, OH) |
Correspondence
Address: |
MARSHALL, GERSTEIN & BORUN LLP
6300 SEARS TOWER
233 S. WACKER DRIVE
CHICAGO
IL
60606
US
|
Family ID: |
32775897 |
Appl. No.: |
10/726044 |
Filed: |
December 2, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60430403 |
Dec 3, 2002 |
|
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Current U.S.
Class: |
220/675 |
Current CPC
Class: |
B29C 2049/4869 20130101;
B65D 2543/00537 20130101; B29C 49/04 20130101; B65D 2543/00101
20130101; B65D 21/0219 20130101; B65D 2543/0074 20130101; B65D
2543/00694 20130101; Y02W 30/80 20150501; B65D 1/22 20130101; B65D
43/0212 20130101; B65D 2543/00648 20130101; B65D 2543/00555
20130101; Y02W 30/807 20150501; B65D 2543/00296 20130101; B65D
2543/00518 20130101; B29L 2031/7126 20130101; B65D 25/2897
20130101; B65D 2543/00805 20130101; B29B 2911/14326 20130101 |
Class at
Publication: |
220/675 |
International
Class: |
B65D 006/28 |
Claims
What is claimed:
1. A storage container comprising: a container portion comprising a
bottom panel connected to and disposed between two opposing bottom
side corner sections and two opposing bottom end corner sections,
each bottom side corner section connecting the bottom panel to one
of two opposing side panels, each bottom end corner section
connecting the bottom panel to one of two opposing end panels, each
side panel being disposed between and connected to the end panels
by one of four vertical corner sections to form an open top box
structure with an interior cargo space and a continuous upper rim,
the four vertical corner sections having an average thickness
greater than an average thickness of at least one of the end panels
or the side panels.
2. The storage container of claim 1 wherein the four vertical
corner sections have an average thickness greater than an average
thickness of the side panels and an average thickness of the end
panels.
3. The storage container of claim 1 wherein the average thickness
of the four vertical corner sections is greater than an average
thickness of the bottom panel.
4. The storage container of claim 1 wherein an average thickness of
the four vertical corner sections is less than an average thickness
of four bottom corner junctions where each vertical corner sections
meets one of the bottom end corner sections and one of the bottom
side corner sections.
5. The storage container of claim 1 wherein the container portion
is formed by a co-extrusion blow molding process.
6. The storage container of claim 1 wherein each of the end panels
further comprises a handle, each handle having an average thickness
greater than the average thickness of at least one of the end or
side panels.
7. The storage container of claim 1 wherein each of the end panels
further comprises a handle, each handle having an average thickness
greater than the average thickness of the end panels and the side
panels.
8. The storage container of claim 1 further comprising a lid, the
lid comprising a top panel disposed between and connected to two
opposing top side corner sections and two opposing top end corner
sections, each top side corner section connecting the top panel to
one of two opposing top side panels, each top end corner section
connecting the top panel to one of two opposing top end panels,
each top side panel being disposed between and connected to the top
end panels by one of four top vertical corner sections to form a
continuous rim for engaging the upper rim of the container portion,
the four vertical top corner sections having an average thickness
greater than an average thickness of at least one of the top end
panels or top side panels.
9. The storage container of claim 8 wherein the four vertical top
corner sections have an average thickness greater than an average
thickness both the top end panels and top side panels.
10. The storage container of claim 8 wherein the average thickness
of the four top vertical corner sections is greater than an average
thickness of the top panel.
11. The storage container of claim 8 wherein an average thickness
of the four top vertical corner sections is less than an average
thickness of four top corner junctions where each top vertical
corner sections meets one of the top end corner sections and one of
the top side corner sections.
12. The storage container of claim 8 wherein the lid is formed by a
co-extrusion blow molding process.
13. A method manufacturing a three dimensional reusable storage
container, the method comprising: providing a parison of polymeric
material; providing a mold comprising a cavity defining a container
portion comprising a bottom panel connected to and disposed between
two opposing bottom side corner sections and two opposing bottom
end corner sections, each bottom side corner section connecting the
bottom panel to one of two opposing side panels, each bottom end
corner section connecting the bottom panel to one of two opposing
end panels, each side panel being disposed between and connected to
the end panels by one of four vertical corner sections to form an
open top box structure with an interior cargo space and a
continuous upper rim; providing an adjustable annular die
comprising an outer peripheral surface and an inner peripheral
surface with a gap disposed therebetween for extruding the parison,
the gap being non-uniform in radial width between the inner and
outer peripheral surfaces, the gap also defining an annular cross
sectional area, the annular cross sectional area being expandable
and contractible by moving the outer peripheral surface closer to
the inner peripheral surface or vice versa, opening the mold;
extruding the parison through the die while moving the outer
peripheral surface of the die closer to the inner peripheral
surface of the die or vice versa so that a plurality of cross
sections of the parison have a non-uniform thickness and further so
that the thickness of the parison is non-uniform along an extruded
length of the parison; closing the mold; inflating the parison
against the cavity of the mold so that the four vertical corner
sections have an average thickness greater than an average
thickness of at least one of the end panels or side panels.
14. The method of claim 13 wherein the inflating of the parison
against the cavity of the mold results in the four vertical corner
sections having an average thickness greater than an average
thickness of the end panels and greater than an average thickness
of the side panels.
15. The method of claim 13 wherein the inflating of the parison
further results in the average thickness of the four vertical
corner sections being greater than an average thickness of the
bottom panel.
16. The method of claim 13 wherein the inflating of the parison
further results in an average thickness of the four vertical corner
sections being less than an average thickness of four bottom corner
junctions where each vertical corner sections meets one of the
bottom end corner sections and one of the bottom side corner
sections.
17. The method of claim 13 wherein the mold cavity further defines
handles disposed on each of the end panels, and wherein the
inflating of the parison further results in each handle having an
average thickness greater than the average thickness of the end and
side panels.
18. The method of claim 13 wherein the mold cavity further defines
a lid, the lid comprising a top panel disposed between and
connected to two opposing top side corner sections and two opposing
top end corner sections, each top side corner section connecting
the top panel to one of two opposing top side panels, each top end
corner section connecting the top panel to one of two opposing top
end panels, each top side panel being disposed between and
connected to the top end panels by one of four top vertical corner
sections to form a continuous rim for engaging the upper rim of the
container portion, wherein the inflating of the parison further
results in the four vertical top corner sections having an average
thickness greater than an average thickness of at least one of the
top end panels or top side panels.
19. The method of claim 18 wherein the inflating of the parison
further results in the four vertical top corner sections having an
average thickness greater than an average thickness of the top end
panels and greater than an average thickness of the top side
panels.
20. The method of claim 18 wherein the inflating of the parison
further results in the average thickness of the four top vertical
corner sections being greater than an average thickness of the top
panel.
21. The method of claim 18 wherein the inflating of the parison
further results in an average thickness of the four top vertical
corner sections being less than an average thickness of four top
corner junctions where each top vertical corner sections meets one
of the top end corner sections and one of the top side corner
sections.
22. A lid for a storage container, the lid comprising: a top panel
disposed between and connected to two opposing top side corner
sections and two opposing top end corner sections, each top side
corner section connecting the top panel to one of two opposing top
side panels, each top end corner section connecting the top panel
to one of two opposing top end panels, each top side panel being
disposed between and connected to the top end panels by one of four
top vertical corner sections to form a continuous rim, the four
vertical top corner sections having an average thickness greater
than an average thickness of at least one of the top end panels or
top side panels.
23. The lid of claim 22 wherein the four vertical top corner
sections have an average thickness greater than an average
thickness both the top end panels and top side panels.
24. The lid of claim 22 wherein the average thickness of the four
top vertical corner sections is greater than an average thickness
of the top panel.
25. The lid of claim 22 wherein an average thickness of the four
top vertical corner sections is less than an average thickness of
four top corner junctions where each top vertical corner sections
meets one of the top end corner sections and one of the top side
corner sections.
26. The lid of claim 22 wherein the lid is formed by a co-extrusion
blow molding process.
27. A method manufacturing a lid for a three dimensional reusable
storage container, the method comprising: providing a parison of
polymeric material; providing a mold comprising a cavity defining a
lid, the lid comprising a top panel disposed between and connected
to two opposing top side corner sections and two opposing top end
corner sections, each top side corner section connecting the top
panel to one of two opposing top side panels, each top end corner
section connecting the top panel to one of two opposing top end
panels, each top side panel being disposed between and connected to
the top end panels by one of four top vertical corner sections to
form a continuous rim; providing an adjustable annular die
comprising an outer peripheral surface and an inner peripheral
surface with a gap disposed therebetween for extruding the parison,
the gap being non-uniform in radial width between the inner and
outer peripheral surfaces, the gap also defining an annular cross
sectional area, the annular cross sectional area being expandable
and contractible by moving the outer peripheral surface closer to
the inner peripheral surface or vice versa, opening the mold;
extruding the parison through the die while moving the outer
peripheral surface of the die closer to the inner peripheral
surface of the die or vice versa so that a plurality of cross
sections of the parison have a non-uniform thickness and further so
that the thickness of the parison is non-uniform along an extruded
length of the parison; closing the mold; inflating the parison
against the cavity of the mold so that the four vertical top corner
sections having an average thickness greater than an average
thickness of at least one of the top end panels or top side
panels.
28. The method of claim 27 wherein the inflating of the parison
further results in the four vertical top corner sections having an
average thickness greater than an average thickness of the top end
panels and greater than an average thickness of the top side
panels.
29. The method of claim 27 wherein the inflating of the parison
further results in the average thickness of the four top vertical
corner sections being greater than an average thickness of the top
panel.
30. The method of claim 27 wherein the inflating of the parison
further results in an average thickness of the four top vertical
corner sections being less than an average thickness of four top
corner junctions where each top vertical corner sections meets one
of the top end corner sections and one of the top side corner
sections.
31. A adjustable die for extruding a parison, the die comprising:
an outer peripheral surface and an inner peripheral surface with a
gap disposed therebetween for extruding the parison, the gap being
non-uniform in radial width between the inner and outer peripheral
surfaces, the gap also defining an annular cross sectional area,
the annular cross sectional area being expandable and contractible
by moving the outer peripheral surface closer to the inner
peripheral surface or vice versa.
32. The adjustable die of claim 31 wherein the outer peripheral
surface of the die is expandable and contractible.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under 35 U.S.C. .sctn.
119(e) of U.S. provisional patent application serial No. 60/430,403
filed Dec. 3, 2002, the disclosure of which is incorporated herein
by reference.
TECHNICAL FIELD
[0002] Improved polymeric reusable storage containers are
disclosed. More specifically, improved reusable storage containers
are disclosed manufactured using a extrusion blow molding process.
Still more specifically, improved reusable storage containers are
disclosed with varying wall thicknesses so that key structural
areas of the container have a greater wall thickness than other
less important structural areas of the container. Still more
specifically, the wall thickness of the container can vary both
axially along a wall and radially across a wall through use of the
disclosed manufacturing process and die apparatus.
BACKGROUND OF THE RELATED ART
[0003] Reusable storage containers are known. Such reusable storage
containers can be fabricated using an extrusion blow molding
process or an injection molding process. FIGS. 1 and 2 illustrate a
container 10 that can be fabricated using a conventional extrusion
blow molding process. Further, FIGS. 3 and 4 illustrate a container
20 that can be manufactured using a conventional injection molding
process. Like reference numerals will be used to refer to like or
similar structural parts for the containers 10 and 20 and these
reference numerals will be used to describe the novel containers
and manufacturing processes of the present invention in the
following sections of this specification.
[0004] The containers include a bottom panel 21 which is connected
to and disposed between two opposing corner sections 22, only one
of which can be seen in FIGS. 1 and 3, and two opposing bottom end
corner sections 23. Each bottom side corner section 22 connects the
bottom panel 21 to one of two opposing side panels 24. Each bottom
end corner section 23 connects the bottom panel 21 to one of two
opposing end panels 25. Further, each side panel 24 is disposed
between and connected to the opposing end panels 25 by one of four
vertical corner sections 26 to form an open box structure as shown
in FIGS. 2 and 4 with a continuous upper rim 27. Further, each
vertical corner section 26 is connected to a bottom end corner
section 23 and a bottom side corner section 22 by a bottom corner
junction 28 (see FIGS. 1 and 3).
[0005] Further each container 10, 20 includes a similar top or lid
31. Each lid 31 includes a top panel 32 disposed between and
connected to opposing top side corner sections, one of which is
shown at 33 in FIG. 3, and two opposing top end corner sections 34.
Each top side corner section 33 connects the top panel to one of
two opposing top side panels 35 (see FIGS. 2-4). Each top end
corner section 34 connects the top panel 32 to one of two opposing
top end panels 36. Each top side panel 35 is disposed between and
connected to the top end panels 36 by one of four top vertical
corner sections 37 (see FIG. 3) to form a continuous rim 38 for
engaging the upper rim 27 of the container portion 41. Each top
vertical corner section 37 is connected to a top side corner
section 33 and a top end corner section 34 by a top corner junction
39 (see FIG. 3). The end panels 25 of the container portion 41 may
also include handles 42.
[0006] As seen in the cross-sectional views provided in FIGS. 2 and
4, the wall thicknesses of the various components, i.e., the end
panels 25, bottom panel 21, bottom end corner sections 23, etc.,
are uniform in thickness. This uniformity in thickness is required
for injection molded containers, like the container 20, as constant
wall thickness is required to minimize adverse flow characteristics
within the mold filling stage, such as incomplete filling of the
mold and trapped air in the mold, both of which can result in
damaged or unusable final products. Further, for extrusion blow
molded products, like the container 10, a constant wall thickness
is also required due to the static nature of the die through which
the parison is extruded.
[0007] However, it would be desirable to produce reusable storage
containers, having similar structural features as the containers 10
and 20 illustrated in FIGS. 1-4 but with a varying wall thickness.
Specifically, it would be desirable to have a greater wall
thickness at key structural areas of the containers 10 and 20, such
as the vertical corner sections 26 and a thinner wall thickness in
less important structural areas such as central areas of the end
panels 25 and side panels 24. Similarly, with respect to the lid
31, it would be useful to be able to manufacture a lid 31 having a
thinner top panel 32 and thicker top vertical corner section 37.
Such containers 10, 20 and lids 31 with varying thicknesses would
provide two benefits. First, structural integrity of the containers
10, 20 and lids 31 would be assured while reducing the overall
weight of the containers 10, 20 and lids 31. Further, material
savings could be achieved thereby reducing the overall cost of the
resultant products.
SUMMARY OF THE DISCLOSURE
[0008] An improved "right-weighted" storage container is disclosed
which comprises a container portion comprising a bottom panel
connected to and disposed between two opposing bottom side corner
sections and two opposing bottom end corner sections. Each bottom
side corner section connects the bottom panel to one of two
opposing side panels. Each bottom end corner section connects the
bottom panel to one of two opposing end panels. Each side panel is
disposed between and connected to the end panels by one of four
vertical corner sections to form an open top box structure with an
interior cargo space and a continuous upper rim. The four vertical
corner sections have an average thickness greater than an average
thickness of at least one of the end panels or the side panels.
[0009] In a refinement, the four vertical corner sections have an
average thickness greater than an average thickness of the side
panels and an average thickness of the end panels.
[0010] In a refinement, the average thickness of the four vertical
corner sections is greater than an average thickness of the bottom
panel.
[0011] In a refinement, an average thickness of the four vertical
corner sections is less than an average thickness of four bottom
corner junctions where each vertical corner sections meets one of
the bottom end corner sections and one of the bottom side corner
sections.
[0012] In a refinement, the container portion is formed by a
co-extrusion blow molding process.
[0013] In a refinement, each of the end panels further comprises a
handle, each handle having an average thickness greater than the
average thickness of at least one of the end or side panels.
[0014] In a refinement, each of the end panels further comprises a
handle, each handle having an average thickness greater than the
average thickness of the end panels and the side panels.
[0015] In a refinement, the container further comprises a lid. The
lid comprises a top panel disposed between and connected to two
opposing top side corner sections and two opposing top end corner
sections. Each top side corner section connects the top panel to
one of two opposing top side panels. Each top end corner section
connects the top panel to one of two opposing top end panels. Each
top side panel is disposed between and connected to the top end
panels by one of four top vertical corner sections to form a
continuous rim for engaging the upper rim of the container portion.
The four vertical top corner sections have an average thickness
greater than an average thickness of at least one of the top end
panels or top side panels.
[0016] In a refinement, the four vertical top corner sections have
an average thickness greater than an average thickness both the top
end panels and top side panels.
[0017] In a refinement, the average thickness of the four top
vertical corner sections is greater than an average thickness of
the top panel.
[0018] In a refinement, an average thickness of the four top
vertical corner sections is less than an average thickness of four
top corner junctions where each top vertical corner sections meets
one of the top end corner sections and one of the top side corner
sections.
[0019] In a refinement, the lid is formed by a co-extrusion blow
molding process.
[0020] A method manufacturing a three dimensional reusable storage
container is disclosed. The method comprises:
[0021] providing a parison of polymeric material;
[0022] providing a mold comprising a cavity defining a container
portion comprising a bottom panel connected to and disposed between
two opposing bottom side corner sections and two opposing bottom
end corner sections, each bottom side corner section connecting the
bottom panel to one of two opposing side panels, each bottom end
corner section connecting the bottom panel to one of two opposing
end panels, each side panel being disposed between and connected to
the end panels by one of four vertical corner sections to form an
open top box structure with an interior cargo space and a
continuous upper rim;
[0023] providing an adjustable annular die comprising an outer
peripheral surface and an inner peripheral surface with a gap
disposed therebetween for extruding the parison, the gap being
non-uniform in radial width between the inner and outer peripheral
surfaces, the gap also defining an annular cross sectional area,
the annular cross sectional area being expandable and contractible
by moving the outer peripheral surface closer to the inner
peripheral surface or vice versa,
[0024] opening the mold; and
[0025] extruding the parison through the die while moving the outer
peripheral surface of the die closer to the inner peripheral
surface of the die or vice versa so that a plurality of cross
sections of the parison have a non-uniform thickness and further so
that the thickness of the parison is non-uniform along an extruded
length of the parison;
[0026] closing the mold;
[0027] inflating the parison against the cavity of the mold so that
the four vertical corner sections have an average thickness greater
than an average thickness of at least one of the end panels or side
panels.
[0028] In a refinement, the inflating of the parison against the
cavity of the mold results in the four vertical corner sections
having an average thickness greater than an average thickness of
the end panels and greater than an average thickness of the side
panels.
[0029] In a refinement, the inflating of the parison further
results in the average thickness of the four vertical corner
sections being greater than an average thickness of the bottom
panel.
[0030] In a refinement, the inflating of the parison further
results in an average thickness of the four vertical corner
sections being less than an average thickness of four bottom corner
junctions where each vertical corner sections meets one of the
bottom end corner sections and one of the bottom side corner
sections.
[0031] In a refinement, the mold cavity further defines handles
disposed on each of the end panels, and wherein the inflating of
the parison further results in each handle having an average
thickness greater than the average thickness of the end and side
panels.
[0032] In a refinement, the mold cavity further defines a lid, the
lid comprising a top panel disposed between and connected to two
opposing top side corner sections and two opposing top end corner
sections, each top side corner section connecting the top panel to
one of two opposing top side panels, each top end corner section
connecting the top panel to one of two opposing top end panels,
each top side panel being disposed between and connected to the top
end panels by one of four top vertical corner sections to form a
continuous rim for engaging the upper rim of the container
portion,
[0033] wherein the inflating of the parison further results in the
four vertical top corner sections having an average thickness
greater than an average thickness of at least one of the top end
panels or top side panels.
[0034] In a refinement, the inflating of the parison further
results in the four vertical top corner sections having an average
thickness greater than an average thickness of the top end panels
and greater than an average thickness of the top side panels.
[0035] In a refinement, the inflating of the parison further
results in the average thickness of the four top vertical corner
sections being greater than an average thickness of the top
panel.
[0036] In a refinement, the inflating of the parison further
results in an average thickness of the four top vertical corner
sections being less than an average thickness of four top corner
junctions where each top vertical corner sections meets one of the
top end corner sections and one of the top side corner
sections.
[0037] A adjustable die for extruding a parison is disclosed. The
die comprises an outer peripheral surface and an inner peripheral
surface with a gap disposed therebetween for extruding the parison,
the gap being non-uniform in radial width between the inner and
outer peripheral surfaces, the gap also defining an annular cross
sectional area, the annular cross sectional area being expandable
and contractible by moving the outer peripheral surface closer to
the inner peripheral surface or vice versa.
[0038] In a refinement, the outer peripheral surface of the die is
expandable and contractible.
[0039] In a refinement, the container and/or lid are manufactured
from polyethylene, such as high density polyethylene. Other
suitable materials for the above-referenced container and lid and
manufacturing methods will be apparent to those skilled in the
art.
[0040] In a further refinement, the lid may be manufactured and
provided separately. Accordingly, the above-disclosed manufacturing
method and adjustable die may be applied to the separate
manufacture of a lid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0041] The disclosed storage container, lid, manufacturing methods
and adjustable die are described more or less diagrammatically in
the accompanying drawings wherein:
[0042] FIG. 1 is a perspective view of a reusable storage container
that can be manufactured using prior art methods as well as the
manufacturing methods disclosed herein;
[0043] FIG. 2 is a sectional view of the container shown in FIG. 1
and further illustrating a lid;
[0044] FIG. 3 is a perspective view of a reusable storage container
including a lid that may be manufactured using prior art methods as
well as the manufacturing methods disclosed herein;
[0045] FIG. 4 is a sectional view of the container and lid
illustrated in FIG. 3;
[0046] FIG. 5 is a sectional view of a mold cavity and die used to
extrusion blow mold improved reusable storage containers and lids
as disclosed herein;
[0047] FIG. 6 illustrates, schematically, the opening of the mold
and the extrusion of the parison during the extrusion blow molding
process disclosed herein;
[0048] FIG. 7 illustrates the mold, parison and die illustrated in
FIG. 6 and further illustrates the pinching of a bottom portion of
the parison with pinch plates;
[0049] FIG. 8 illustrates the mold, parison, die and pinch plates
of FIG. 7 but with the mold closed just prior to the inflation of
the parison;
[0050] FIG. 9 is a perspective, sectional and schematic view of the
closed mold and parison after inflation of the parison against the
mold cavity;
[0051] FIG. 10 is a schematic illustration of a shaped die for use
in the manufacturing processes disclosed herein;
[0052] FIG. 10A is a partial sectional view of the shaped die shown
schematically in FIG. 10;
[0053] FIG. 11 is a graphical representation of three shaped dies
used in the manufacturing processes disclosed herein;
[0054] FIG. 12 is a schematic illustration of a parison extruded
through the shaped die of FIG. 10;
[0055] FIG. 13 is a schematic illustration of the parison of FIG.
12 that has been extruded and inflated against a mold cavity;
[0056] FIG. 14 illustrates, graphically, variation in thickness of
a parison along an axial length of the parison used in the
manufacturing methods disclosed herein;
[0057] FIG. 15 is a schematic illustration of a parison with
varying thickness along the axial length thereof;
[0058] FIG. 16 illustrates, schematically, the parison of FIG. 15
after inflation against a mold cavity; and
[0059] FIG. 17 is a schematic illustration of a parison that has
been extruded through an adjustable shaped die, similar to the one
shown in FIG. 10 but which has been adjusted during the extrusion
of the die to vary the annular gap between the inner and outer die
plates to vary the thickness of the parison both radially and along
the axial length of the parison.
[0060] It should be understood that the drawings are not
necessarily to scale and that the embodiments are illustrated by
graphic symbols, phantom lines, diagrammatic representations and
fragmentary views. In certain instances, details which are not
necessary for an understanding of the disclosed containers, lids,
manufacturing methods and adjustable dies and other details
difficult to perceive may have been omitted. It should be
understood, of course, that this disclosure is not necessarily
limited to the particular embodiments illustrated herein.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
[0061] Improved methods for manufacturing storage containers like
those shown at 10 and 20 and lids like that shown at 31 in FIGS.
1-4 will be described in detail below. To decrease the weight of
the containers 10, 20 and lids 31 without sacrificing structural
integrity, the above containers 10, 20 and lids 31 are manufactured
so that an average wall thickness at the vertical corner sections
26 is greater than an average wall thickness at the side panels 24
and/or end panels 25. The containers 10, 20 are manufactured so
that an average wall thickness at the bottom corner junctions 28 is
greater than an average wall thickness of the side panels 24 and
end panels 25. Further, these key structural areas 26, 28 can have
a greater average wall thickness than that of the bottom panel 21.
Still further, an average wall thickness of the bottom side corner
sections 22 and/or bottom end corner sections 23 can have a greater
average wall thickness than that of the side panels 24 and/or end
panels 25. Also, the bottom side corner sections 22 and/or bottom
end corner sections 23 can have a greater average wall thickness
than that of the bottom panel 21.
[0062] Similarly, the lid 31 can be manufactured in a similar
manner. Specifically, the top vertical corner sections 37 can have
a greater average wall thickness than that of the top panel 32. The
top vertical corner sections can have a greater average wall
thickness than that of the top side panels 35 and/or top end panels
36. Further, the top side corner sections 33 and/or top end corner
sections 34 can have a greater average wall thickness than that of
the top panel 32 and/or the top side panels 33 and/or the top end
panels 36.
[0063] By utilizing the various guidelines set forth above, the
overall weight of the containers 10, 20 can be reduced without
adversely affecting the structural integrity thereof. Further,
substantial material cost savings will result.
[0064] Turning to FIG. 5, a mold 50 is disclosed with cavities 51,
52 for manufacturing two separate containers. A die is shown
schematically at 53. Turning to FIG. 6, a parison 54 is extruded
through the die 53 through conventional means. However, the die 53
is a shaped die and an adjustable die as described below. The mold
50 has been opened during the extrusion of the parison 54. Turning
to FIG. 7, the pinch plate 55 is closed on a bottom end 56 of the
parison 54. As shown in FIG. 8, after extrusion of the parison 54
enclosure of the pinch plate 55, the mold 50 is closed and an
injection pin or other means for inflating the parison 54 is
inserted through the parison. As shown in FIG. 9, the parison is
inflated against the mold cavities 51, 52 to provide two molded
containers.
[0065] The containers preferably have an irregular or non-uniform
wall thickness. This is achieved in two ways. First, by providing a
shaped die 53 as illustrated in FIGS. 10 and 10A. As shown in FIGS.
10 and 10A, the die 53 includes an outer peripheral surface 61, an
irregular inner peripheral surface 62 and an irregular annular gap
63 disposed therebetween. The outer peripheral surface 61 is an
essentially circular or cylindrical surface. However, the surface
of the inner peripheral surface 62 is non-cylindrical and therefore
a parison extruded through the gap 63 has a thickness that is
non-uniform radially or, in other words, a cross-section of the
parison has a non-uniform thickness for varying the wall thickness
radially around or partially across the wall surfaces of the
resultant container 10, 20. FIG. 11 provides a graphical
representation of various gap 63 thicknesses that can be provided
with dies of structures similar to those shown in FIGS. 10 and 10A.
The die 53 of FIGS. 10 and 10A, without adjusting the size of the
outer peripheral surface 61 as discussed below, will provide a
parison schematically illustrated at 65 in FIG. 12. Inflation of
the parison will result in containers formed as shown in FIG. 3
with wall segments 66a-66g of varying thicknesses. Thus, the die 53
as shown in FIGS. 10 and 10A can be used to fabricate containers
10, 20 with vertical corner sections 26 that are thicker than end
panels 25 and side panels 24.
[0066] To vary the thickness of the parison along an axially length
of the parison, the outer surface 61 can be moved closer to or
farther away from the inner surface 62 during extrusion of the
parison through the gap 63. Preferably, the die includes a
contractible and expandable structure 67 for this purpose. It will
also be noted that the structure 68 which provides the inner
peripheral surface 62 can also be expandable and contractible, the
design of such a structure would be complicated due to the
irregular surface 62. Thus, by expanding and contracting the outer
surface 61, a parison 70 as shown in FIG. 15 can be provided with
discreet segments 71a-71n of varying thicknesses which, when
inflated will produce the containers shown in FIG. 16, also having
a varying wall thickness along the length of the containers. FIG.
14 illustrates, graphically, how the die gap opening 63 can be
varied during extrusion of a parison to vary the parison wall
thickness as it is extruded through the die 53.
[0067] Finally, to vary the wall thickness of the parison, and
consequently, the wall thickness of the parison after inflation, or
the wall thickness of the resulting container, both radially, that
is circumferentially around the container, and axially, that is,
along the length or height of the, container, an adjustable shaped
die is utilized with an irregular inner surface 62 and expandable
and contractible outer surface 61 which can produce a parison 75 as
shown in FIG. 17. By utilizing both die shaping, i.e., a shaped or
irregular inner surface 62, along with parison programming, i.e.,
varying the cross-sectional area of the die gap 63 during extrusion
of the parison, the parison like the one shown at 75 in FIG. 17 can
be extruded that has a varying wall thickness both radially, or
cross-sectionally, and axially, or along a length of the parison
75. Thus, the parison 75 can be utilized to fabricate containers
10, 20 with thicker walls at key structural points, such as the
vertical corner sections 26, bottom corner junctions 28 and handles
42 and thinner wall sections at the less important structural areas
such as the side panels 24, end panels 25 and bottom panels 21.
Similarly, lids can be fabricated using the extrusion blow molding
processes disclosed herein with greater wall thicknesses at the top
vertical corner sections 37, top corner junctions and reduced wall
thicknesses at least important structural areas such as the top
panel, top side panels and top end panels. Obviously, an infinite
number of variations in wall thicknesses from discreet area to
discreet area of each container 10, 20 and lid 31 can be provided.
All such variations are intended to fall within the spirit and
scope of this disclosure.
* * * * *